1. Field of the Invention
The present invention relates to an electronic apparatus, and more particularly, to an electronic apparatus and a positioning device handling positioning information, a processing method in the electronic apparatus and the positioning device, and a program allowing a computer to perform the method.
2. Description of the Related Art
Recently, imaging apparatuses such as digital still cameras and digital video cameras (for example, camera-integrated recorders) that generate image data by imaging a subject such as a person or a landscape and recording the generated image data as an image content (image file) are widely used. In addition, imaging devices capable of recording the generated image data in association with the position at the time of imaging are proposed. For example, imaging apparatuses that have a GPS (Global Positioning System) device and record positional information acquired by the GPS device in association with generated image data are proposed.
In addition, recently, miniaturized imaging apparatuses that can be easily taken along by a user are widely used. Many of such portable imaging apparatuses are operated with battery driving, and it is important to lengthen the operating time thereof. Accordingly, even in acquisition of positional information using a GPS device, methods of suppressing the power consumption thereof are proposed.
Here, in a case where positional information is acquired by a GPS device, a time necessary for positioning differs in accordance with information (orbital information (ephemeris data), time information, and the like) maintained in the GPS device. For example, in a case where the GPS device maintains the ephemeris data and the time information, the GPS device can perform positioning by being started up through a hot start using the maintained information. On the other hand, in a case where the GPS device does not maintain the ephemeris data, the GPS device performs positioning by being started up through a cold start or a warm start using the maintained information. In other words, in a case where the ephemeris data is not maintained but the time information is maintained, the GPS device performs positioning by being started up through a warm start. In addition, in a case where any of the ephemeris data and the time information is not maintained, the GPS device performs positioning by being started up through a cold start.
While the hot start has relatively short time (about several seconds) that is necessary from the start-up to position measurement, the cold start and the warm start have relatively long time (30 seconds or longer) that is necessary from the start-up to position measurement. Accordingly, in a case where the positional information is desired to be acquired in a speedy manner after the start-up of the GPS device, it is important to maintain a state in which the device can be started up through the hot start. However, the effective time of the ephemeris data is four hours. Furthermore, since satellites that are seen form the same location change about every two hours, generally, the effective time of the ephemeris data is two hours.
Thus, for example, an information processing apparatus that monitors the photographing frequency and controls the supply of power to the GPS device based on the photographing frequency is proposed (for example, Japanese Unexamined Patent Application Publication No. 2007-155577 (FIG. 1)). This information processing apparatus, for example, intermittently supplies power to the GPS device in a case where the photographing frequency is less than a predetermined threshold value and continuously supplies power to the GPS device in a case where the photographing frequency is equal to or greater than the predetermined threshold value.